Effect of dorsal capsular imbrication on intraoperative DRUJ instability following arthroscopic TFCC repair surgery

Background To assess the clinical outcomes and identify the ideal indication for implementing dorsal distal radioulnar joint (DRUJ) capsular imbrication after triangular fibrocartilage complex (TFCC) repair in cases of DRUJ instability. Methods We conducted a retrospective study on patients who underwent arthroscopic TFCC repair between 2016 and 2021. Inclusion criteria comprised a symptomatic ulna fovea sign for over 6 months and dorsal DRUJ subluxation on magnetic resonance imaging. A total of 225 patients were divided into two groups: Group 1 (135 cases) with a negative ballottement test after “Cross-form TFCC repair” (CR) and Group 2 (90 cases) with a positive ballottement test after “Cross-form TFCC repair” and augmented DRUJ stability through dorsal DRUJ capsular imbrication (CR + DCI). Pain visual analog scale score (VAS), grip strength, modified Mayo Wrist Score (MMWS), wrist range of motion (ROM), and patient-reported outcomes (PROMs) were assessed for a minimum of 3 years postoperatively. Results Both groups showed significant improvements in pain VAS score, grip strength, wrist ROM, MMWS, and PROMs between the preoperative and postoperative periods (all P < 0.05). Recurrent DRUJ instability occurred in 3.7% and 1.1% of patients in the “CR” and “CR + DCI” groups, respectively, with a significant difference. Despite the “CR + DCI” group initially exhibiting inferior ROM compared with the “CR” group, subsequently, no significant difference was noted between them. Conclusions Dorsal DRUJ capsular imbrication effectively reduces postoperative DRUJ instability rates, enhances grip strength, and maintains wrist ROM in patients with a positive intra-operative ballottement test after arthroscopic TFCC repair.


Introduction
Distal radioulnar joint (DRUJ) stability during unrestricted forearm rotation relies on several factors, including the integrity of the triangular fibrocartilage complex (TFCC), the interosseous membrane, the bony configuration of the sigmoid notch, DRUJ capsule, and the extensor carpi ulnaris tendon with its subsheath [1].TFCC injury often results from a fall on the outstretched, pronated, and hyperextended wrist, leading to dorsal instability of the DRUJ [2].
Within the anatomical structure of the TFCC, the fovea ulnaris serves as the convergent point of proximal component TFCC (pc-TFCC) insertion, thereby becoming the most indispensable stabilizer for the ulnocarpal joint and DRUJ [3].Based on the ulnar-side TFCC tear in Palmar type Ib, Atzei et al. [4].classified the treatment-oriented TFCC peripheral tear into five subgroups depending on whether the distal component (dc-TFCC) or the pc-TFCC was involved.Specifically, Atzei class II and III indicate DRUJ instability with complete and pc-TFCC rupture, respectively [5].Consequently, the current approach for foveal-involved TFCC tear aims at achieving anatomical TFCC foveal reattachment, which can be accomplished through transosseous sutures [6][7][8] or suture anchor fixation [4,9,10] and has shown satisfactory outcomes.
A prior study revealed that even when radiography findings are negative in patients experiencing posttraumatic wrist pain, 42% of them receive a diagnosis of TFCC injuries [3].and neglecting severe TFCC tears often leads to chronic DRUJ instability.According to tissue-engineering theory, the interface of bone-to-ligament may not regenerate after injury, resulting in a high rupture recurrence rate [11], and direct bone-to-ligament repair in the chronic stage might exhibit decreased healing potential with the disadvantageous repair margin [12].Compared with transosseous sutures, transcapsular repair, involving ligament-to-capsular healing, is an alternative method for addressing TFCC fovea tear [13].
In particular, research has supported the notion that transcapsular repair alone can stabilize the DRUJ while achieving anatomical restoration of the dorsal subluxation of the ulna head [13,14].
However, the integrity of DRUJ surrounding tissues, such as dorsal and volar radioulnar ligaments (DRUL and VRUL) with a superficial and a deep portion attached to the dorsal capsule, needs to be considered after the completion of TFCC repair [15].For instance, Liu et al. [16].reported post-operative DRUJ instability rates of 12.1% with capsular repair and 10.1% with fovea transosseous repair.Consequently, additional procedures to reinforce DRUJ stability may be necessary.
The dorsal capsular imbrication (DCI) technique has been proposed and reported to yield positive clinical results in chronic DRUJ dislocation cases [17][18][19][20][21][22][23][24][25].However, the use of DCI as a reinforcement procedure in TFCC repair operations for chronic DRUJ instability has not been extensively studied.Therefore, this study aimed to evaluate the surgical outcomes of DCI in patients with a positive intra-operative ballottement test (grade I, II, III) after completing TFCC repair.We hypothesize that this procedure is a safe and reliable treatment option for refractory DRUJ instability in arthroscopic TFCC repair operations.

Patient enrolment
This study adhered to the tenets of the Helsinki Declaration and was approved by the Research Ethics Committee of China Medical University Hospital, Taichung, Taiwan (IRB number: CMUH112-REC2-144).We retrospectively reviewed patients with repairable TFCC (Atzei II, III) injuries who underwent arthroscopic "cross-form" trancapsular repair with or without dorsal DRUJ capsular imbrication from January 2016 to January 2021.A minimum follow-up period of 36 months was mandatory for inclusion.The exclusion criteria encompassed patients with non-repairable TFCC (Atzei IV) ulnar and DRUJ osteoarthritis changes (Atzei V).All procedures were performed by a senior hand surgeon.

Clinical and image assessment
Pre-operatively, patients were diagnosed via a series of physical examinations, including ulna fovea sign, pushoff test, and ballottement test for DRUJ laxity [18].Wrist X-rays were employed to assess bony structure malalignment, such as ulnar styloid fracture, ulna variance, distal radius fracture or Galeazzi fracture [26].Additionally, magnetic resonance imaging (MRI) of the wrist was performed to evaluate the condition of articular cartilage wear, detect foveal TFCC tear, and identify ulna head subluxation [27].

Arthroscopic assessment
Radiocarpal joint arthroscopy was performed using a 3/4 viewing portal (2.7-mm arthroscopy), a 6R working portal (equipped with a synovial shaver and probe), and a 6U portal (utilized as a fluid outflow portal).The 3/4 viewing portal allows the visualization of the dc-TFCC lesion over the ulnar margin of the TFCC.Through the 6R portal, a probe was used to perform a hook test, and a shaver served as a suction test to evaluate the pc-TFCC condition.Notably, in cases where the pc-TFCC was challenging to assess using the aforementioned tests, especially if dc-TFCC was intact (Atzei III), a direct foveal (DF) portal was established.Then, the interposed fibrous and scar tissue were debrided completely with the shaver, burr and radiofrequency device.The tourniquet was deflated to check the peripheral vascularization of the TFCC foveal region; after confirming adequate debridement, the tourniquet was inflated again.
Before suturing, a 2-cm incision was made over the 6U portal.The dorsal cutaneous branch of the ulnar nerve (DCBUN) and flexor carpi ulnaris (FCU) tendon were identified and retracted.The first horizontal mattress suture involved a 2 − 0 ethibond stitch close to the volar-ulnar margin of the TFCC lesion through the 3/4 portal using an inside-out technique (Fig. 1A) and subsequently retracted to avoid DCBUN and FCU involvement (Fig. 2A).The second stitch, a 2 − 0 prolene lasso loop suture, was performed near the dorsal-radial margin of the intact TFCC part through the 6R portal using an outside-in technique.The lasso loop suture carried one end of the 2 − 0 ethibond to form the first horizontal mattress suture (Fig. 1B).For the second horizontal mattress suture, the puncture site of the third stitch was performed close to the volar-radial margin of the TFCC intact part through the 3/4 portal with an inside-out technique (Fig. 1C), and the DCBUN should be protected from being punctured or tied in this step (Fig. 2B).The fourth stitch, a lasso suture, was performed near the dorsal-ulnar margin of the TFCC lesion through the 6R portal using an outside-in technique.The lasso loop suture was then used to carry one end of the third stitch to form the second horizontal mattress suture (Fig. 1D).This "cross-form" TFCC capsular repair created an extensive contact area in the ligament to capsule suture (Fig. 3).
After completing two horizontal mattress sutures, the wrist traction tower device was released and firmly tied in the wrist's full-pronation position (Fig. 1E).Both sutures were checked to ensure they were tied below the ECU, FCU and DCBUN to avoid neuro-tendon involvement (Fig. 2C), achieved by reducing the ulnar head from dorsal subluxation into a neutral position using thumb compression by an assistant (Fig. 1F).

Part 2: intra-operative ballottement test
We employed the intra-operative ballottement test to assess DRUJ stability after completing the "Cross-form" TFCC transcapsular repair, categorizing it into four grades: (a) Grade 0: Normal stability (Fig. 4A).In cases where normal stability is detected, the "Cross-form" TFCC transcapsular repair alone is assumed to provide sufficient DRUJ stability.(b) Grades 1-3: If there is laxity greater than grade 0 in the intraoperative ballottement test after tightening the strings following TFCC repair, dorsal DRUJ capsular imbrication is performed to stabilize the DRUJ [30].

Part 3. Dorsal DRUJ capsular imbrication
A 4-cm curved incision, distance between these two wounds will be at least 3 cm (Fig. 5), was made along the extensor digiti minimi (EDM) tendon extending proximally to the proximal margin of the DRUJ.Meticulously dissection of subcutaneous tissue was performed, with attention to the dorsal branch of the ulnar nerve.
Following the longitudinal incision of the extensor retinaculum, the fourth and fifth extensor compartments were retracted ulnarly and radially, respectively.Subsequently, the dorsal DRUJ capsule was opened and incised longitudinally.
In cases of chronic DRUJ instability, the dorsal capsule often exhibited looseness and weakness due to repetitive dorsal stretching by the ulnar head (Fig. 6A).A rectangular capsule flap, approximately 2 × 2.5 cm 2 and ulnarbased, was carefully dissected from the dorsal cortex of radius bone, extending from the radial to ulnar direction, and exposing the radius sigmoid notch and ulnar head (Fig. 6B).To enhance the healing potential of DRUJ capsule-to-bone connection, the dorsal cortex of distal radius was decorticated using a rongeur.Two 1.4 allsuture bone anchors (JuggerKnot; Zimmer Biomet, Warsaw, IN) were individually placed radially over the upper and lower borders of the distal radius sigmoid notch (Fig. 6B).
Subsequently, with the elbow flexed at 90º and the forearm in a straightened position with full pronation, the assistant digitally pressed the dorsally displaced ulnar head, lowering it back into the sigmoid notch.The operator then imbricated the detached radius-and ulnar-based capsule flap by tightening sutures from the bone anchors (Fig. 6C).This maneuver stabilized the ulna head in a secured position (Fig. 6D).
The patient was protected with a long-arm cast, with the forearm in a neutral position, for the first 4 weeks postoperatively.After cast removal, passive three-dimensional (3D) wrist motions were initiated with wrist brace protection from 5 to 8 weeks postoperatively.Low-intensity muscle strengthening exercises were introduced from weeks 9-12 postoperatively.

Postoperative course and follow-up
The patient's profile, time interval from injury to surgery, and intra-operative and post-operative complications were documented based on the medical charts.The push-off test and ballottement test were employed to evaluate the ulnar-side pain relief and DRUJ stability, respectively.At postoperative intervals of 3, 6, 9, 12, 24, and 36 months, active motion arcs were measured using a goniometer and grip strength was measured with the Jamar Hydraulic Hand Dynamometer (Jamar Technologies/America, Hatfield, PA).
Additionally, patient-reported outcomes, including MMWS, Patient-Rated Wrist Evaluation (PRWE), and Disabilities of the Arm, Shoulder, and Hand (DASH) were used.The proportion of patients meeting the minimal clinically important difference (MCID) of the DASH (MCID: 10-13.5)and PRWE scores (MCID: 14-17) allowed for the quantitative recording of the direct feelings of the patients [31].

Post hoc power analysis
In our prior comparative research [20], the mean ± standard deviation of wrist range of motion (ROM), with respect to pronation and supination, was found to be 161 ± 13.6º, and 156 ± 12.6º in the "dorsal capsular imbrication" group and the "TFCC repair + dorsal capsular imbrication" group, respectively.Based on a statistical power of 80% and a significance level of 5%, we determined that a minimum of 90 cases for group 1 and 90 cases for group 2 were necessary to ascertain whether a true difference in clinical outcomes existed between both groups.

Statistical analysis
All data were analyzed using SPSS software (version 20.0;IBM Corp., Armonk, NY).The Shapiro-Wilk test showed that the data were normally distributed; therefore, parametric tests were employed for comparison.Categorical variables were presented as frequency (%).The Chi-squared test was used for parametric statistical analysis of categorical information, and the independent sample T test was employed for parametric analysis of continuous variables.To compare outcome measurements between two groups (DASH score, PRWE score, grip strength, and ROM), the Wilcoxon rank sum test was used.Statistical significance was set at P < 0.05.

Results
From January 2016 to June 2021, a total of 265 patients underwent surgical treatment for post-traumatic chronic DRUJ instability at our hospital.Among them, those excluded from the study were 29 patients who underwent DRUJ reconstruction due to Atzei class IV or V TFCC tear, 4 with radioulnar joint arthritis, 7 lost to follow-up, along EDM; At least 3 cm distance between 6R portal and 6U portal.Legends: Green color: 6U portal (wound for part 1 "Cross-form" TFCC transcapsular repair).Blue color: 6R portal (wound for part 3 dorsal DRUJ Capsular Imbrication).Red color: distance between 6R portal and 6U portal and 4 who had prior wrist surgery.Ultimately, a total of 225 patients were included in our final analysis.Among them, 110 had Atzei class II and 115 had Atzei class III TFCC tears, and all underwent arthroscopy-assisted TFCC capsular repair with dorsal DRUJ capsule imbrication (Fig. 7).
Comparison of post-operative results between Group 1 and Group 2 are shown in Table 4.Our findings revealed that in the mid-term (post-operative 1 year to 3 years), the "CR + DCI" group continued to demonstrate superior grip strengths compared with the "CR" group (Table 4).However, no significant difference was observed in all directions of wrist ROM between the two groups at the post-operative 3-year follow-up (Table 4).
Post-operative complications included that recurrent DRUJ instability, which occurred in 3.7% (5/135) and 1.1% (1/90) in Group 1 and Group 2, respectively, with a significant difference between the two groups.Also, the transient dorsal sensory branch of the ulnar nerve (DSBUN) irritation was noted with 2.9% (4/135) and 2.2% (2/99) in Group 1 and Group 2, separately with no significant difference between the two groups (Table 4).

Discussion
The primary finding of our study is that incorporating DCI in TFCC repair for patients with a positive intraoperative ballottement led to a very low post-operative instability rate.Compared with patients who underwent TFCC repair alone (due to intraoperative negative ballottement test), those who received DCI as an augmentation demonstrated significantly higher grip strength, short-term decreased wrist ROM, and long-term comparative ROM.
Recent studies comparing DRUJ stability after capsular repair and transosseous repair have produced varying results: Ruch et al. [38] demonstrated no significant difference, while Johnson et al [39].indicated greater stability with transosseous repair.However, the critical factor for successful TFCC repair lies in the healing potential of the contact surface, w6hich is notably poor in ligamentto-bone repair (fovea repair): 1. Ulna fovea has a "band shaped"-like footprint [40], whereas "suture anchor repair" and "transosseous tunnel repair" only provide a point contact area between the TFCC remnant and the ulna fovea; 2. " Enthesis" refers to the insertion site of a tendon, ligament or joint capsule into bone [41].Fovea repair, "transooseous repair" or "suture anchor repair, " requires the reattachment of TFCC remnant parts into the ulna fovea.Few vessels penetrate the enthesis due to a calcified barrier [42].In contrast, capsular repair may be more effective in enhancing the healing potential of the TFCC through ligament-to-capsule repair compared to [43] ligament-to-bone repair.However, a comprehensive review involving 825 cases across 30 studies revealed post-operative distal radioulnar joint (DRUJ) instability rates of 12.1% for capsular repair and 10.1% for fovea transosseous repair.Regarding re-operation rates, they were 7.9% for capsular repair and 5.5% for fovea transosseous repair [16].These results indicate that intraoperative instability of the DRUJ can be a concern in both primary methods of TFCC repair.Therefore, employing an intraoperative DRUJ stability test could be essential for identifying potential postoperative instability and the failure of TFCC repair.Augmentation with DCI can help prevent postoperative DRUJ instability and the need for subsequent reoperation.
The intra-operative ballottement test is a simple method for evaluating DRUJ stability after arthroscopic TFCC repair.A positive result suggests that the strength of the repaired TFCC alone may be insufficient to maintain DRUJ stability.DCI can be employed as a supplementary method to enhance DRUJ stability.Using DCI as a sole treatment for patients with DRUJ instability has been successful in restoring DRUJ stability in 97.8% of cases, with 93.6% of patients experiencing pain relief through this approach [17][18][19][20][21][22][23][24][25].In a long-term study spanning 10 years, it was observed that DCI effectively restored wrist function to levels comparable to the contralateral hand.DCI can also function as a secondary stabilizer, following a similar bridging concept to that of the internal brace used in anterior talofibular ligament [44] or knee medial collateral ligament repair [45].When combined with the suture tap and bone anchors, it can reinforce ligament strength and prevent injury recurrence during the rehabilitation process [44].Similarly, DCI can restore intact DRUJ kinematics and radioulnar ligament reconstructions in chronic DRUJ instability [46].In the present study, recurrent DRUJ instability was found to be significantly lower in patients with the augmentation of DCI, compared to 3.7% and 1.1% in "CR" group 1 and "CR + DCI" group 2, with a significant difference.Thus, we believe that DCI could be an effective method for addressing intraoperative DRUJ instability following TFCC capsular repair.
In this treatment protocol, we aim to outline the procedures necessary to restore the integrity of TFCC and DRUJ capsules: (1) "TFCC capsular repair" combines the benefits of the inside-out and outside-in techniques, reducing the cut-through rate, purchasing the wide contact area between the ulna fovea and adhering TFCC remnant part with the surrounding tissue to reinforce the DRUJ stability.The crux of transcapsular repair is the ligament-to-soft tissue healing process.Therefore, nonabsorbable suture 2 − 0 ethibond was selected to provide reliable tension support.(2) "intra-operative Ballottement test" checked the integrity of the DRUJ stability, grade 0 indicates that "TFCC transcapsular repair" was sufficient to maintain DRUJ stability, while grade I, II or III suggests that DRUJ laxity or subluxation existed after transcapsular repair, and the subsequent augmentation for DRUJ stability was needed, (3) "Dorsal DRUJ capsular imbrication" tightening the redundant laxity of dorsal DRUJ capsule, reducing the subluxation of ulna head and reattaching the DRUL to the tightened DRUJ capsule under wrist full-pronation position.Tension of the imbricated capsule can be optimized to stabilize DRUJ with the utilization of two suture anchors over the dorsal cortex of the radius sigmoid notch.Our results indicated a slightly higher rate of postoperative distal radioulnar joint (DRUJ) instability in Group 1, which underwent only TFCC capsular repair, compared to Group 2, which received both TFCC capsular repair and dorsal DRUJ capsular imbrication.This implies that late DRUJ instability may manifest in patients who initially tested negative in the intraoperative ballottement test but only underwent TFCC repair.It also implies that DCI is a reliable procedure to build up the DRUJ stability.
A major concern about our methods was that there was no wrist stiffness found in the "CR + DCI group" compared with "CR" group" in the post-operative 3 years following.Additionally, the grip strength of "CR + DCI group" showed significantly better than that of "CR" group".Another issue to consider is that the transient neuropathy occurred in 2.7% (6/225) patients due to dorsal sensory branch of ulnar nerve (DSBUN) needed to be retracted and protected during tying knot process; however, sensory irritation will subside within 2 weeks postoperatively.

Limitations
This study has few limitations.First, it focused solely on surgical outcomes and functional measures, lacking postoperative axial MRI to verify the repositioned DRUJ.Second, being a retrospective comparative study with post-operative 3 years follow-up, a longer-term investigation is needed to validate the observed clinical outcomes.Third, the intraoperative ballottement test employed in this study remains subjective.Future studies should consider standardizing pull strength and translation distance measurements to enhance the accuracy of identifying subtle cases of DRUJ instability following TFCC repair.Finally, we did not include a control group comprising patients with persistent instability after TFCC repair who did not receive additional treatment to enhance DRUJ stability.However, establishing such a control group presented ethical and clinical challenges, as leaving untreated cases of persistent DRUJ instability was not considered feasible.

Conclusions
Our findings revealed that in chronic cases of DRUJ instability with ulna fovea tear, "Cross form" TFCC repair may be employed to restore DRUJ stability.Specifically, if the intra-operative ballottement test indicates residual DRUJ instability following TFCC capsular repair, "Dorsal capsular imbrication" can be applied to augment DRUJ stability.This procedural protocol serves as a viable treatment option for patients experiencing chronic DRUJ instability.

Table 1
Patients demographic and clinical characteristics b : Cross-form repair + Dorsal capsular imbrication

Table 2
Cross-form repair group: 135 cases (pre-operative vs. post-operative 3 years) c : Disabilities of the Arm, Shoulder, and Hand PRWE d : Patient-Rated Wrist Evaluation

Table 4
Cross-form repair group vs. cross-form repair + dorsal capsular imbrication group (post-operative 3 years) f : Dorsal sensory branch of the ulnar nerve CR g : Cross-form repair CR + DCI h : Cross-form repair + Dorsal capsular imbrication